This application claims priority of application No. 2000-43279 filed in the Korean Industrial Property Office on Jul. 27, 2000, the content of which is incorporated hereinto by reference.
(a) Field of the Invention
The present invention relates to a stem for a cathode ray tube, in which shapes of stem mounds are differentiated according to loads applied to inner leads so that cracks of the stem mounds and apertures blocking of a shadow mask due to the crack particles may be prevented.
(b) Description of the Related Art
In general, a cathode ray tube is a display for realizing a certain image by a phosphor screen with electron beams which are emitted from an electron gun, wherein a stem is mounted with a plurality of leads for fixing the electron gun in a bulb and connecting the electrodes of the electron gun to an external set circuit, so as to apply a predetermined voltage signal to the respective electrodes of the electron gun.
As shown in FIG. 1, a related art cathode ray tube includes a face panel 1, a funnel 3 and a neck portion 5 which are integrally sealed and constitute a bulb 7, wherein the face panel 1 is formed with a phosphor screen 9 on an inner surface and is mounted with a shadow mask 11 at a predetermined distance from the phosphor screen 9, the funnel 3 has a deflection yoke 13 mounted on an outer peripheral surface, and the neck portion 5 has an electron gun 15.
In the structure as above, as the electron gun 15 emits three electron beams to their corresponding red R, green G and blue B phosphor layers, the electron beams are deflected by magnetic fields which are generated by the deflection yoke 13 and form a raster on the phosphor screen 9. The raster is divided into the corresponding R, G and B phosphor layers in the phosphor screen 9 by the shadow mask 11 serving as an color-selecting electrode, so that precise colors are displayed.
The electron gun 15 includes a cathode for emitting electrons, and a plurality of electrodes for forming an electronic lens by a potential difference and controlling focusing and acceleration degree of the electrons, wherein the cathode and the plurality of electrodes are connected to respective leads 19 which are attached to a stem 17 to be supplied with voltage signals from an external set circuit.
FIG. 2 is a front view of a related art stem and FIG. 3 is a plane view of the stem.
Referring to FIG. 2 and FIG. 3, the stem 17 includes a stem part 21 in the shape of a circular disc to be integrally melted with an end of the neck portion 5, an exhausting tube 23 mounted in the middle of the stem part 21 for connecting an inside of the bulb 7 to an unshown exhausting system, a plurality of leads 25 mounted along a periphery of the exhausting tube 23 and connected to the respective electrodes of the electron gun 15, and a plurality of stem mounds 27 for fixing and supporting the respective leads 25 to the stem part 21.
The leads 25 are divided into two parts, of which inner leads 25a are positioned inside the neck portion 5 with relation to the stem mounds 27 to be connected to the electron gun 15 and outer leads 25b are positioned outside the stem mounds 27 to be connected to the external set circuit.
According to the above structure, the inner leads 25a of the stem 17 are welded to the respective electrodes of the electron gun 15 directly or via an additional connection conductor, so that the stem 17 is integrated with the electron gun 15. The neck portion 5 and the stem part 21 are heated and melted together by a well-known torch heating method under the state that the stem 21 is facing to an end of the neck portion 5 to facilitate insertion of the electron gun 15 into the neck portion 5.
After fixing the stem 17 to the neck portion 5, the exhausting system is driven to evacuate an inside of the bulb 7 by means of the exhausting tube 23, and the inside of the bulb 7 is sealed in a high vacuum state after melting the exhausting tube 23 by the torch heating method, and cutting it.
As described above, the stem 17 is integrally joined to the neck portion 5 for serving to support the electron gun 15 in the bulb 7, wherein the plurality of leads 25 and the stem mounds 27 which fix and support the leads 25 are formed to have a same diameter and shape, so that the plurality of inner leads 25a and the stem mounds 27 have the same load intensity characteristics.
The inner leads 25a are, however, applied with a bending deformation stress due to the load and welding of the electron gun 15, since the whole melting and discharging procedure of the stem 17 and the neck portion 5 is carried out under the circumstances that the electron gun 15 is fixed in the stem 17, and particularly, the load is not uniformly applied to all the inner leads 25a but is concentrated on some of the inner leads 25a which support the electron gun 15.
Therefore, cracks are apt to be generated at the load-concentrated leads 25a due to the high load, so that the supporting force of the leads 25 becomes decreased due to the cracks, and beam passing apertures of the shadow mask 11 are blocked by glass powder which is generated in the stem mounds 27 and advances into the bulb 7.
Such an apertures blocking of the shadow mask 11 disturbs passage of the electron beams and accordingly the phosphor screen 9 can not emit light, resulting in the formation of a black spot at a certain position.
It is an object of the present invention to provide a stem for a cathode ray tube in which stem mounds are reinforced to prevent cracks from being generated therein to accordingly prevent blockage of apertures of a shadow mask caused by glass powder from the cracks.
In order to achieve this object, the stem for a cathode ray tube includes a stem part of a circular disc type to be integrally sealed with an end of a neck portion, an exhausting tube mounted in the middle of the stem part for the exhausting of a bulb, a plurality of leads mounted to the stem part along a periphery of the exhausting tube and connected to respective electrodes of an electron gun for providing voltage signals, and a plurality of stem mounds mounted to the respective leads for fixing and supporting the leads on the stem parts and having different shapes depending on loads to be applied to the leads, wherein some of the stem mounds have an increased diameter as the loads applied to their corresponding leads increase.
In the stem for a cathode ray tube of the present invention, cracks of the stem mounds and the apertures blocking of the shadow mask due to the crack particles are effectively prevented.